The long range goal of this project is to study the oxidation of chemicals to toxic or carcinogenic metabolites by prostaglandin H synthase (PHS) and to demonstrate the importance of this enzyme system in chemical-induced toxicity or carcinogenesis. We have shown that aromatic amine carcinogens, are metabolized to mutagens by PHS. PHS dependent oxidation occurred by a free radical mechanism and resulted in the formation of DNA adducts which can be used as in vivo markers for PHS- dependent oxidation. We have further studied the formation of amine mutagens by PHS using bacterial tester systems having different levels of acetylase activity. Our data indicate that acetylase plays an important role in the formation of free radical mutagens from aromatic amines, including bladder carcinogen such as benzidine derivatives. We have also examined the interaction between bisulfite oxidation and the carcinogen benzo[a] pyrene (BP) =7,8-diol. Enhanced epoxidation is observed but the formation of sulfonates of BP-7,8-diol are seen in the reaction of sulfur trioxide anion radical with BP-7,8-diol. We further studied peroxidase catalyzed GSH conjugate formation and showed that this reaction occurs with a number of chemicals that contain a conjugated double bond adjacent to a aromatic ring. The reaction appears to be a general mechanism for conjugate formation. We have also shown that P-450 metabolites of BP will enhance this reaction which serves as a mechanism for detoxication of carcinogens. We have also started a new study on the dealkylation of aromatic amines by peroxidases using as model compounds the calcium ion indicator Quin-2 and its analogues. Our investigation of the activation of the heterocyclic aromatic compounds by PHS has continued. Our data suggest that PHS is a versatile enzyme system that can catalyze a variety of reactions which are important in the conversion of chemicals to carcinogenic metabolites in extra hepatic tissue.
